Bodengebundene Fernerkundung von Eiswolken im nahen Infrarot

In dieser Arbeit werden die Möglichkeiten zur bodengebundenen Fernerkundung des ef- fektiven Radius R.¡¡ und der optischen Dicke rc.¿ vol Eiswolken im nahen Infraroten untersucht. Unter der Voraussetzung einer optisch dünnen Eiswolke wurden die Fak- toren gesucht, die in den für diesen Fall wichtigen spektralen Kanälen (1046 nm wd 7550 nm, in atmosphårischen Fenstern) einen Einfluß auf die Abschätzung dieser Größen haben könnten. Ein spektral und räumlich hoch auflösendes Spektrometer wurde in drei F äilen für die Messung der an unterschiedlichen Eiswolkenarten vorwärtsgestreuten Strah- lung eingesetzt. Wolkenlose Spektren können erfolgreich von bewölkten getrennt werden. Wenn hexagonale säulenartige Kristalle in Eiswoiken überwiegen, kann fúr R.¡¡ > 25p,m der effektive Radius von Eiswolken mit Hilfe der optischen Eigenschaften von Kugeln abgeschätzt werden. Aus dem Vergleich der bodengebundenen Messungen mit Strah- lungstransportrechnungen wurde R"JÍ für drei unterschiedliche Meßfälle zwischen 1 und 200p,m abgeschätzt. Durch die Abschätntngvon R"¡¡ aus den Messungen konnten so- wohl eine zeitliche Entwicklung der Mikrophysik von Cirren und Kondenstreifen hin zu größeren effektiven Radien als auch eine Zunahme der Partikelgröße mit der optischen Dicke bei Eiswolken festgestellt werden. Zur Abschätnng der optischen Dicke der Eis- wolke aus vorwärtsgestreuten Strahldichten ist die Kenntnis der mittleren Kristallform oder der dazugehörigen Phasenfunktion notwendig. Mit Hilfe eines der Meßfälle wurde gezeigt, daß zur Ableiiung der optischen Dicke des Aerosols die optischen Eigenschaften von klimatologisch gemittelten Aerosoltypen nicht immer ausreichend sind

Electromagnetic N->Delta transition and neutron form factors

The C2/M1 ratio of the electromagnetic N->Delta(1232) transition, which is important for determining the geometric shape of the nucleon, is shown to be related to the neutron elastic form factor ratio G_C^n/G_M^n. The proposed relation holds with good accuracy for the entire range of momentum transfers where data are available.Comment: 4 pages, 2 figure

An exploratory study on the impact of physical training on police recruits’ self-efficacy in handling violent encounters

Police officers are often required to use physical force to effectively protect themselves as well as the public. In order to prepare officers for these physical demands, recruits receive training in fitness and defensive tactics during their Police Academy instruction. The present study aimed to develop a reliable scale for measuring an officer’s self-efficacy and used the scale to evaluate the impact of the Academy training on recruits’ self-efficacy. Most of the participants credited the academy control tactics (98.5%) and fitness training (88.1%) with improving their self-efficacy. These results support the importance of physical training curricula at improving recruit officers’ self-efficacy toward handling violent encounters prior to entering the law enforcement workforce

Pion-nucleus optical potential valid up to the DELTA-resonance region

We present in this article an optical potential for the $\pi$-nucleus interaction that can be used in various studies involving $\pi$-nucleus channels. Based on earlier treatments of the low energy $\pi$-nucleus optical potential, we have derived a potential expression applicable from threshold up to the $\Delta$-resonance region. We extracted the impulse approximation form for this potential from the $\pi-N$ scattering amplitude and then added to it kinematical and physical corrections. The kinematic corrections arise from transforming the impulse approximation expression from the $\pi-N$ center of mass frame to the $\pi$-nucleus center of mass frame, while the physical corrections arise mostly from the many-body nature of the $\pi$-nucleus interaction. By taking advantage of the experimental progress in our knowledge of the $\pi-N$ process, we have updated earlier treatments with parameters calculated from state-of-the-art experimental measurements.Comment: 23 pages, 12 figures. Accepted for publication in Physical Review

Hard Exclusive Pion Electroproduction at Backward Angles with CLAS

We report on the first measurement of cross sections for exclusive deeply virtual pion electroproduction off the proton, ep→e′nπ+, above the resonance region at backward pion center-of-mass angles. The φπ⁎-dependent cross sections were measured, from which we extracted three combinations of structure functions of the proton. Our results are compatible with calculations based on nucleon-to-pion transition distribution amplitudes (TDAs). These non-perturbative objects are defined as matrix elements of three-quark-light-cone-operators and characterize partonic correlations with a particular emphasis on baryon charge distribution inside a nucleon. Keywords: TDA, Exclusive single pion, Eletroproduction, CLA

First Results on Nucleon Resonance Photocouplings from the γp → π+π−p Reaction

We report the first experimental measurements of the nine 1-fold differential cross sections for the γ p → π+π−p reaction, obtained with the CLAS detector at Jefferson Laboratory. The measurements cover the invariant mass range of the final state hadrons from 1.6 GeV \u3c W \u3c 2.0 GeV. For the first time the photocouplings of all prominent nucleon resonances in this mass range have been extracted from this exclusive channel. Photoproduction of two charged pions is of particular importance for the evaluation of the photocouplings for the Δ (1620)1/2−, Δ (1700)3/2−, N(1720)3/2+, and Δ (1905)5/2+ resonances, which have dominant decays into the π π N final states rather than the more extensively studied single meson decay channels